TheSeattle Mariners made headlines last week when they reportedly agreed to a five-year extension with ace Felix Hernandez worth $135.5 million. The contract, however, is not finalized yet and the ongoing negotiations will cause Hernandez to skip the upcoming World Baseball Classic and now it seems the contract has even more ground to cover before its a done deal as the condition of Hernandez’s throwing elbow has become a concern.

King Felix has been a workhorse throughout his career in Seattle, throwing 1620 1/3 innings already at just 26-years-old. Only three other pitchers have thrown as many innings as Hernandez before their 27th birthday in the history of MLB, and only one, Bert Blyleven, went on to enjoy a long Hall of Fame career. The other two, Fernando Valenzuela and Dwight Gooden, ended up flaming out before their time.

With baseball contracts being fully guaranteed and salaries climbing every year, teams are becoming warier of potential health risks during contract negotiations. Nothing sinks a team faster than being on the hook for a monster contract to a player who can’t take the field. For the Mariners, this elbow is “an issue,” according to sources.

One possible solution is to add language that would protect Seattle from major injury during the length of the contract. The New York Yankees included similar language when they agreed on an extension with CC Sabathia 16 months ago which protected the team in the event of a shoulder injury before the end of the deal.

The team needs to find some way to get the deal done, however, quickly. The Mariners want to lock up their franchise player throughout his prime and Hernandez has said he wants to remain in Seattle for his entire career. The longer negotiations drag on, however, the greater the chance the whole thing falls apart and Hernandez decides to to take his talents elsewhere.

Things are still looking optimistic for the King to keep his court in Safeco Field for years to come, but until the deal is done, nothing is guaranteed.